Until now, optically transparent, dye-doped solids have been in the form of large crystals, inorganic glasses, and polymers. For reviews of inorganic glasses, see, e.g.: a.) Struct. Bond 1996, 85 (complete volume); b) Lebeau, B.; Sanchez, C. Current Opinion in Solid State and Materials Science 1999, 4, 11; c) Dunn B.; Zink, J. Chem. Mater. 1997, 9, 2280; d) Avnir, D. Acc. Chem. Res. 1995, 28, 328. For polymers, see, e.g: Qian, S.-X.; Snow, J. B.; Tzeng, H.-M.; Chang, R. K. Science 1986, 231, 486. In each of these systems, there are limitations to the incorporation of optically responsive compounds or other property restrictions that constrain their utility for device applications. For example, the inclusion of optically responsive agents in crystalline solids is limited to low concentrations, because of disruptions to the crystalline lattices. In glasses, aggregation of dye species occurs at relatively low dye-doping levels (above˜0.5 wt %) to produce undesirable opacity or high excitation thresholds for lasing or amplified spontaneous emission. See, e.g: Yanagi, H.; Hishiki, T.; Tobitani, T.; Otombo, A.; Mashiko, S. Chem. Phys. Lett. 1998, 292, 332. Polymeric systems are frequently limited by relatively low thermal or mechanical stabilities, especially with regard to the photostability of the incorporated dye (e.g., the decomposition of the dye under light illumination), which is crucial to long term device reliability and operation. See Rahn, M. D.; King, T. A. Appl. Opt. 1995, 34, 8260.
Because of the favorable properties of sol-gel glasses in terms of processing and dye photostability compared to polymeric host systems, substantial efforts have been undertaken to characterize the properties of the included dye species and to optimize syntheses for optical applications. The spectroscopic properties of such dye-host materials are mainly determined by the local dye environment, which can be used to probe local dye interactions with the host matrix. Numerous dye-doped sol-gel-derived glasses with different compositions and prepared under different processing conditions (pH, solvent used, sol-gel aging time) have been investigated. See Struct. Bond, supra; Lebeau, B.; Sanchez, C., supra; Dunn B.; Zink, J., supra; and Avnir, D. Acc., supra. Two primary means by which the spectroscopic properties of such materials can be modified are through changes in the composition of the host matrix or through the selection of different optically responsive species. One example is the use of organically modified silicate systems (so-called ORMOSILS), instead of an entirely inorganic oxide matrix, to prepare organic-dye-doped systems with enhanced photostabilities. See, e.g.: Zink, J. I.; Dunn, B.; Kaner, R. B.; Knobbe, E. T.; McKiernan, J. ACS Symp. Ser. 1991, 398, 541. A second example is the incorporation of rare earth complexes as luminescent species in composites of sol-gel glasses and organic polymers to reduce non-radiative quenching by H2O or inorganic hydroxyl groups, thereby enhancing quantum efficiencies and light emission. See Bekiari, V.; Pistolis, G.; Lianos, P. J. Non-cryst. Solids 1998, 226, 200. Local dye environments are crucially important to the optical properties of dye-doped solids and it would be desirable to be able to adjust such nanoscopic structural and compositional features with greater control and efficiency.
Dye-doped sol-gel-derived glasses have been important in the development of optical materials exhibiting lasing or amplified spontaneous emission (ASE) properties and in the development of optically based sensors. Lasing and amplified spontaneous emission have been demonstrated in such systems processed as monoliths and as thin films. For monoliths, see Zink, J. I. et al, supra, and e.g.: Salin, F.; Le Saux, G.; Georges, P.; Brun, A.; Bagnall, C.; Zarzycki, J. Opt. Lett. 1989, 14, 785. For thin films, see Yanagi, H., et al, supra. However, the thresholds for both kinds of superlinear optical input-output behavior tend to be undesirably high, due to relatively low dye solubilities and low quantum efficiencies (as discussed in more detail below). Such systems have nevertheless been used to develop optically based sensors for acidity, oxygen gas, and heavy metal detection. See, e.g: pH sensing : Grattan, K. T. V.; Badini, G. E.; Palmer, A. W.; Tseung, A. C. C. Sensors and Actuators 1991, 25-27, 483; Lobnik, A.; Oehme, I.; Markovic, I.; Wolfbeis, O. S. Anal. Chim. Acta 1998, 367, 159; Ben-David, O.; Shafir, E.; Gilath, I.; Prior, Y.; Avnir, D. Chem. Mater. 1997, 9, 2255; Rottman, C.; Ottolenghi, M.; Zusman, R.; Lev, O.; Smith, M.; Gong, G.; Kagan, M. L.; Avnir, D. Mater. Lett. 1992, 13, 293; Yang, L.; Saavedra, S. S. Anal. Chem. 1995, 67, 1307; oxygen sensing: McEvoy, A. K.; McDonagh, C.; MacCraith, B. D. J. Sol-Gel Sci. Techn. 1997, 8, 1121; McDonagh, C.; MacCraith, B. D.; McEvoy, A. K. Anal. Chem. 1998, 70, 45; heavy metal sensing: Iosefzon-Kuyavskaya, B.; Gigozin, I.; Ottolenghi, M.; Avnir, D.; Lev, O. J. Non-cryst. Solids 1992, 147&148, 808.
While good long-term stabilities and processabilities of dye-doped inorganic glasses or ORMOSIL materials are attractive for sensing applications, a major drawback is their relatively long response times. This is due to the dense homogeneous material structures in which the optically responsive species are encapsulated that slow diffusive transport of target molecular species to the optically responsive sensing sites within the material. The best sensing response times reported for dye-doped inorganic glasses or ORMOSIL are slow: ˜5 s for oxygen sensing with ruthenium complexes or ˜20 s for pH sensing using fluorescein-derivatives.
Recently, the use of self-assembling surfactant species to organize inorganic networks has provided opportunities to produce inorganic/organic composites and mesoporous solids with high degrees of mesoscopic order. So far, interest in these materials, which can have large surface areas of up to ˜1400 m2/g (after oxidation/extraction of the surfactant species,) has been confined mainly to catalysis and separation applications, because they have been prepared predominantly as powders. See Bunker, B. C.; Rieke, P. C.; Tarasevich, B. J.; Campell, A. A.; Fryxell, G. E.; Graff, G. L.; Song, L.; Liu, J.; Virden, J. W.; McVay, G. L. Science 1994, 264, 48; Sayari, A. Chem. Mater. 1996, 8, 1840; and Corma, A. Chem. Rev. 1997, 97, 2373. However, based on recent processing advancements, transparent mesostructured/mesoporous systems have been prepared. See Ryoo, R.; Ko, C. H., Cho, S. J., Kim J. M., J. Phys. Chem. B, 1997, 101, 10610; Huo, Q.; Zhao, D.; Feng, J.; Weston, K.; Buratto, S. K.; Stucky, G. D.; Schacht, S.; Schueth, F. Adv. Mater. 1997, 9, 974; Zhao, D.; Yang, P.; Melosh, N.; Feng, J.; Chmelka, B. F.; Stucky, G. D. Adv. Mater. 1998, 10, 1380; Yang, P.; Zhao, D.; Chmelka, B. F.; Stucky, G. D. Chem. Mater. 1998, 10, 2013; Goeltner, C., Henke, S., Weissenberger, M. C., Antonietti, M., Angew. Chem., Int Ed. Engl., 1998, 37, 613; Melosh, N. A.; Lipic, P.; Bates, F. S.; Wudl, F.; Stucky, G. D.; Fredrickson, G. H.; Chmelka, B. F. Macromolecules 1999, 32, 4332; Melosh, N. A.; Davidson, P.; Chmelka, B. F. J. Am. Chem. Soc. 2000, 122, 823; and Yang, P.; Wirnsberger, G.; Huang, H. C.; Cordero, S. R.; Scott, B; McGehee, M. D.; Deng, T.; Whitesides, G. M.; Chmelka, B. F.; Buratto, S. K.; Stucky, G. D. Science 2000, 287, 465.
Optical functionalities have been introduced into such structures. See Yang, P. et al, supra, Marlow, F.; McGehee, M. D.; Zhao, D.; Chmelka, B. F.; and Stucky, G. D. Adv. Mater. 1999, 11, 632. Such functionalities can be introduced using surfactants with optical functionalities, reactive oxide/surfactant interfaces for the assembly of silicon clusters, or the covalent anchoring of dyes in small-pore thin films and monoliths. For surfactants, see Zhou, H. S.; Honma, I. Adv. Mater. 1999, 11, 683. For oxide/surfactant interfaces, see: Dag, O.; Ozin, G. A.; Yang, H.; Reber, C.; Bussiere, G. Adv. Mater. 1999, 11, 474. For covalent anchoring, see Lebeau, B.; Fowler, C. E.; Hall, S. R., Mann S. J. Mater. Chem. 1999, 9, 2279; and Fowler, C. F.; Lebeau, B.; Mann, S. Chem. Commun. 1998, 1825.
Thus far, however, no optical or sensing applications of these materials have been demonstrated, beyond amplified spontaneous emission (ASE) from small unit-cell mesostructured micron-size particles (grown by two-phase synthesis) and ASE in patterned thin films. [Marlow, F. et al, supra, and Yang, P., et al, supra.] Additionally, the successful removal of the surfactant, simultaneously maintaining both mesostructural order and optical transparency, has until now not been demonstrated. Distinct advantages of mesostructured/mesoporous materials over the prior art for several applications will be shown and discussed below.
Mesostructured/mesoporous materials have attracted a great deal of interest as potential catalysts and separation media, because of their large pore dimensions and volumes and high internal surface areas. See, Yanagiswa, T.; Shimizu, T.; Kuroda, K.; Kato, C. Bull. Chem. Soc. Jpn. 1990, 63, 988; Kresge, C. T.; Leonowicz, M. E.; Roth, W. J.; Vartuli, J. C.; Beck, J. S. Nature, 1992, 359, 710; Beck, J. S.; Vartull, J. C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.; Schmitt, K. D.; Chu, C. T.-W.; Olson, D. H.; Sheppard, E. W.; McCullen, S. B.; Higgins, J. B.; Schlenker, J. L. J. Am. Chem. Soc. 1992, 114, 10834; Bunker, B. C.; Rieke, P. C.; Tarasevich, B T; Campell, A. A.; Fryxell, G. E.; Graff, G. L.; Song, L.; Liu, J.; Virden, J. W.; McVay, G. L. Science, 1994, 264, 48; Sayari, A. Chem. Mater. 1996, 8, 1840; and Corma, A. Chem. Rev. 1997, 97, 2373.
As indicated above, interesting application possibilities exist for mesoscopically ordered composites as optical materials, particularly as host media for molecules and complexes exhibiting optical functionalities. [Huo, Q.; Zhao, D.; Feng, J.; Weston, K.; Buratto, S. K.; Stucky, G. D.; Schacht, S.; Schüth, F. Adv. Mater. 1997, 9, 974.] Such materials, with symmetric and adjustable mesoscopic structures and compositions, offer new opportunities for controlling the local environments of occluded dye molecules. Until now, dye inclusion has been mainly restricted to either incorporation in pure oxides or polymeric hosts. For oxides, see e.g., Avnir, D.; Levy, D.; Reisfeld, R. J Phys. Chem. 1984, 88, 5956; Salin, F.; Le Saux, G.; Georges, P.; Brun, A.; Bagnall, C.; Zarzycki, J. Opt. Lett. 1989, 14, 78; McKiernan, J. M.; Yamanaka, S. A.; Dunn, B.; Zink, J. I. J Phys. Chem. 1990, 94, 5652; and Yanagi, H.; Hishiki, T.; Tobitani, T.; Otomo, A.; Mashiko, S. Chem. Phys. Lett. 1998, 292,332. For polymeric hosts, see e.g., Deshpande, A.; Namdas, E. B. Chem. Phys. Lett. 1996, 263, 449; Kuwata-Gonokami, M.; Takeda, K.; Yasuda, H.; Ema, K. Jpn. J. Appl. Phys. 1992,31, L99; Taniguchi, H.; Yamada, H.; Fujiwara, T.; Tanosaki, S.; Ito, H.; Morozumi, H.; Baba, M. Jpn. J. Appl. Phys. 1993, 32, L59; and Kamada, K.; Sasaki, K.; Misawa, H.; Kitamura, N.; Masuhara, H. Chem. Phys. Lett. 1993, 210, 89.] An exception, as indicated above, is the occlusion of dyes in ORMOSILs, which have been shown to allow structural tuning of the local dye environment to a certain degree. However, such dye-doped ORMOSIL materials show no evidence of crystalline or mesoscopic ordering, as measured by X-ray or electron diffraction [Zink, J. I.; Dunn, B.; Kaner, R. B.; Knobbe, E. T.; McKiernan, J. ACS Sym. Ser. 1991, 455,541; and Knobbe, E. T.; Dunn, B.; Fuqua, P. D.; Nishida, F. Appl. Opt. 1990, 29, 2729.] Very recently, sol-gel glasses have also been doped with surfactants and their use has been shown to influence substantially the spectroscopic properties of simultaneously occluded dye molecules. [Rottman, C.; Grader, G.; Hazan, Y. D.; Melchior, S.; Avnir, D. J Am. Chem. Soc. 1999, 121, 8533.]
The degree of control over dye molecule environments and other advantages (such as increased photostability of occluded dye species), is expected to be significantly enhanced in dye-doped mesostructured composites. Furthermore, it is likely that new synergistic effects might result from surfactant/dye co-assembly into mesoscopically ordered structures. The use of differently charged surfactants (non-ionic, cationic, anionic) and the possibility of preparing structures under basic, neutral, or acidic conditions offers versatile synthesis and processing conditions that can be used to tailor materials to desired properties. See, Behrens, P. Angew. Chem. Int. Ed. Engl. 1996, 35, 515; Huo, Q.; Margolese, D. I.; Stucky, G. D. Chem. Mater. 1996, 8, 1147; Huo, Q.; Margolese, D. I.; Ciesla, U.; Feng, P.; Gier, T. E.; Sieger, P.; Leon, R.; Petroff, P. M.; Schueth, F.; Stucky, G. D. Nature 1994, 368, 317; Huo, Q.; Marg-Jese, D. I.; Ciesla, U.; Demuth, D. G.; Feng, P.; Gier, T. E.; Sieger, P.; Firouzi, A.; Chmelka, B. F.; Schueth, F.; Stucky, G. D. Chem. Mater. 1994, 6, 1176; and Bagshaw, S. A.; Prouzet, E.; Pinnavaia, T. J. Science 1995, 269, 1242.
Silica mesostructured materials synthesized under acidic conditions, below the pH 2 isoelectric point of silica have proved to be particularly promising [Huo, Q.; Nature; and Zhao, D.; Science] in that they can be rapidly processed into different morphologies (fibers, films, monoliths) and hierachically ordered structures patterned by soft-lithography. For reviews of soft-lithographic patterning, see Xia, Y.; Whitesides, G. M. Ann. Rev. Mater. Sci. 1998, 28,153; Xia, Y.; Rogers, J. A.; Paul, K. E.; Whitesides, G. M. Chem. Rev. 1999, 99, 1823. For fibers, see Huo, Q.; Zhao, D., et al, supra; Yang, P.; Zhao, D., et al, supra; and Bruinsma, P. J.; Kim, A. Y.; Liu, J.; Baskaran, S. Chem. Mater. 1997, 9, 2507. For thin films, see Lu, Y.; Ganguli, R.; Drewien, C. A.; Anderson, M. T.; Brinker, C. J.; Gong, W.; Guo, Y.; Soyez, H.; Dunn, B.; Huang, M. H.; Zink, J. I. Nature 1997, 389, 364; Tolbert, S. H.; Schaffer, T. E.; Feng, J.; Hansma, P. K.; Stucky, G. D. Chem. Mater. 1997, 9, 1962; Aksay, I. A.; Trau, M.; Manne, S.; Honma, I.; Yao, N.; Zhou, L.; Fenter, P.; Eisenberger, P. M.; Gruner, S. M. Science 1996, 273, 892; Yang, H.; Kupernan, A.; Coombs, N.; Mamiche-Afara, S.; Ozin, G. A. Nature 1996, 379, 703; Ryoo, R.; Ko, C. H.; Cho, S. J.; Kim, J. M. J Phys. Chem. B 1997,101,10610; and Zhao, D.; Yang, P.; Melosh, N.; Feng, J.; Chmelka, B. F.; Stucky, G. D. Adv. Mater. 1998, 10, 1380. For monoliths, see Melosh, N. A.; Lipic, P.; Bates, F. S.; Wudl, F.; Stucky, G. D.; Fredrickson, G. H.; Chmelka, B. F. Macromolecules 1999, 32, 4332; and Goeltner, C., Henke, S., et al, supra. For hierachically ordered structures, see Yang, P.; Deng, T.; Zhao, D.; Feng, P.; Pine, D.; Chmelka, B. F.; Whitesides, G. M.; Stucky, G. D. Science 1998, 282, 2244; Zhao, D.; et al. Adv. Mater. (meso/macroporous membranes). Synthesis conditions can moreover be adapted to allow such materials to be prepared over a wide range of inorganic framework compositions and mesoscopic structures to tailor the properties of these complex heterogeneous multicomponent systems. [Yang, P.; Deng, T., et al, supra; and Huang, M. H.; Dunn, B. S.; Soyez, H.; Zink, J. I. Langmuir 1998, 14, 7331.
Whereas the first incorporation of dye molecules into mesostructured materials was aimed at in situ monitoring of mesostructure formation during processing [Lu, Y., et al, supra; and Zhou, H. S.; Honma, I., et al, supra], recent efforts have been directed toward the goal of obtaining dye-doped structures for optical applications. [Honma, I.; Zhou, H. S.; Chem. Mater. 1998, 10, 103.] Quite different approaches have been used, ranging from the incorporation of phthalocyanins with the help of specifically designed surfactants,[Wu, J.; Gross, A. F.; Tolbert, S. H. J Phys. Chem. B 1999, 103, 2374] or insertion of polymers into MCM-41-type materials after surfactant extraction, [Dag, O.; Ozin, G. A.; Yang, H.; Reber, C.; Bussiere, G. Adv. Mater. 1999,11, 474] to the generation of photoluminescent silicon clusters on the walls of as-synthesized SBA-3 films. [Yang, P.; Wirnsberger, G., et al, supra.] We have recently reported the development of patterned waveguide arrays formed from rhodamine-6G-doped mesostructured silica using poly(ethyleneoxide)-b-(poly(propyleneoxide)-b-poly(ethyleneoxide) amphiphilic triblock copolymer surfactant species [specifically, (EO)20(PO)70(EO)20, abbreviated P123]. [Yang, P. et al., Science, 2000, XX, XX.] Rhodamine-6G (R6G)-doped mesostructured silica composites were formed into long nonintersecting line patterns by using soft lithography.
Here, we disclose and characterize mesostructured inorganic-organic composite and porous inorganic materials for optical and sensing applications. Such materials have several important advantages and properties including unique adjustability of material composition, structure, macroscopic morphologies, and orientational ordering. This permits substantial improvements (e.g., lower lasing thresholds, higher photostabilities, and superior mechanical and thermal stabilities) over the existing state-of-the-art in several areas, including waveguides, lasers, optical limiters, optical switches and interconnects, optical amplifiers, and sensing devices.